Basic creep in concrete at an early age plays an important role in the mechancal properties of young concrete and many researches on this field have been carried out. According to recent some studies, however, it is the conclusion that for some cases the basic creep measured from the sealed concrete specimen shows inaccurate results. More specifically, for high-strength concrete (HSC), the incorrectness is more apparent due to autogenous shrinkage occurred at an early age. This paper shows the results obtained from experimental study to evaluate the effect of autogenous shrinkage on basic creep. In this study, four different mixture proportions of which primany test variable is water-cement ratio (w/c) were placed and autogenous shrinkage and basic creep tests on the specimen were performed with age and various loading levels. From this research, it was found that the differences between apparent creep and real creep were remarkable in HSC at an early age. Therefore, it is recommended to modify existing basic creep model equation by considering autogenous shrinkage.

유동화 콘크리트의 건조수축 및 크리프 특성을 검토하기 위하여 유동화제 2종류와 일반감수제 1종류를 사용하여 재하 하중조건(압축강도의 15% 및 30%)별, 양생조건별로 압축강도 및 건조수축을 측정하고 기건상태하의 크리프 및 크리프변형을 측정하여 유동화 콘크리트의 장기 변형특성을 검토하였다. 그 결과, 유동화 콘크리트는 보통 콘크리트에 비하여 재령 28일의 압축강도는 약 22% 증가하였고, 건조수축은 15% 감소하였으며, 크리프변형은 약 11% 감소하였고 28일간의 크리프회복은 보통 콘크리트에 비하여 작음을 알 수 있었다. 따라서 사용목적에 따른 적절한 유동화제의 선택과 적정량의 유동화제 사용은 건조수축 및 크리프변형에 효과적인 것으로 판단된다.

Mathematical models of shrinkage and creep are based on the experimental evidences obtained from the ideal laboratory environment. In case of the age-dependent behavior of RC beam, the shrinkage strain may not be uniform through the depth of beam whereas it has been usually assumed to be uniform through the beam depth. This paper addresses the assumption of uniform shrink\age strain through the beam depth and flexural creep that has been observed from the recent test program.